Longitudinal Changes in Optic Nerve Head Blood Flow in Normal Rats Evaluated by Laser Speckle Flowgraphy.

Purpose: To investigate longitudinal changes in mean blur rate (MBR) measured by laser speckle flowgraphy (LSFG) in the rat optic nerve head (ONH), and the reproducibility of MBR.

Methods: Rats were dilated under general anesthesia. Intraocular pressure (IOP), blood pressure, ocular perfusion pressure (OPP), heart rate, and LSFG were measured 30 minutes later. Mean blur rate in the ONH was determined using LSFG-Micro and was subdivided into MBR of the total area (MA), vessel region (MV), and tissue region (MT). Mean blur rate measurements were repeated at 10, 11, 13, 19, and 20 weeks, then every 5 weeks until 60 weeks of age. Intrasession repeatability, intrasession reproducibility, and intersession reproducibility were evaluated.

Results: Coefficient of variation of MBR was 0.3 to 6.2%, 1.3 to 5.2%, and 5.8 to 30.4% for intrasession repeatability, intrasession reproducibility, and intersession reproducibility, respectively. Mean blur rate of the total area, MV, and MT increased similarly until 19 weeks of age, but stabilized thereafter until 60 weeks. Mean blur rate of the total area in the inferior quadrant was significantly higher than in the temporal quadrant from 19 to 55 weeks. These changes exceeded a range of corresponding coefficient of reproducibility. There were no significant changes in IOP, blood pressure, or OPP during the experimental period.

Conclusions: Mean blur rate in the rat ONH changed over time, increased from 10 to 19 weeks of age, then stabilized until 60 weeks. Mean blur rate of the total area exhibited regional differences: higher in the inferior quadrant than in the temporal quadrant. Laser speckle flowgraphy-Micro may provide reliable information for evaluating longitudinal changes of rat ONH blood flow.